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Genus Helianthus (Sunflower)

Helianthus Helianthus annuus Photo/Illustration: Michelle Gervais
hee-lee-AN-thus Common Name: Sunflower
This genus contains annuals and perennials native to North, Central, and South America. Sunflowers are generally coarse plants with simple, bristly leaves. Their showy flowers are daisy-shaped and, thanks to many cultivars, come in shades of yellow, orange, red, cream, purple, and bronze.
Noteworthy characteristics: Showy, daisy-shaped flowers in a vast array of sunny colors, forms, and sizes. Good in borders, annual beds, cutting gardens, and wildlife plantings.
Care: Sunflowers need full sun and fertile, moist but well-drained soil. They flower best during long, hot summers. Most will tolerate drier conditions, but some species thrive in moist soil. Stake if needed.
Propagation: Sow seeds of annuals in late winter indoors or in situ in spring. Sow seeds of perennials in a cold frame in spring. Divide perennials in spring or fall or root basal cuttings in spring.
Problems: Downy mildew, powdery mildew, canker, rust, and fungal leaf spots are common. Be on the lookout also for caterpillars, cutworms, beetles, and weevils.

Species, varieties and cultivars for genus Helianthus

Helianthus angustifolius Helianthus angustifolius
(Swamp sunflower)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

A profusion of golden yellow flowers appears for two to three weeks starting in early autumn. Daisy-like flowerheads are 3 inches across with 15 to 20 yellow ray florets radiating from a flat-topped purple or dark brown cone. The entire plant looks like a giant flame, drawing the attention of gardeners and many species of butterflies, bees, and other nectar feeders.

Helianthus annuus and cvs. Helianthus annuus and cvs.
(Sunflower)
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Sunflowers are some of the easiest plants to start from seed. They are available in numerous cultivars which span the range of heights, flower colors, and form.

Helianthus debilis Helianthus debilis
(Branching sunflower)
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These branching plants with thick stems and glossy mid-green leaves grow 5 to 6 feet tall. Slightly nodding flowerheads 2.5 inches or more across appear in summer. Bright yellow ray florets are sometimes flushed with red or purple-red disk florets.

no image available Helianthus divaricatus
(Woodland sunflower)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

July through September, this sunflower bears golden yellow flowerheads with 8 to 9 ray florets around darker orange-yellow disk florets. Stems are tall and hairy; lance-shaped mid-green leaves are rounded at the base, appearing in opposite pairs.

Helianthus grosse-serratus Helianthus grosse-serratus
(Sawtooth sunflower)
(1 user review)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Sawtooth sunflower's abundant yellow daisy flowers bloom from late summer well into fall. The dark green, narrow leaves have a leathery gloss. A well-behaved plant, sawtooth sunflower forms a thick, slowly expanding clump. It can reach 10 feet and taller, depending on conditions.